Talking about the scheme, Ch Insp Butler said: "We are confident that this will give us more evidence and a better understanding of how the spit guards would work across the force to protect those involved in handling extremely difficult detainees."

He said the extension includes all custody suites and one team in each of our four geographical areas: Hull, east Yorkshire, northern Lincolnshire and north-east Lincolnshire.

Humberside Police said it had used spit hoods twice during the initial pilot scheme, with the process being recorded and reviewed, and put before an independent scrutiny panel.

Ch Insp Butler said the force would review any evidence before making a decision on a further roll-out of the guards. The extended pilot will run for three months.